A precise understanding of the biochemical mechanisms by which the somatotrope synthesizes, stores and releases growth hormone is a necessary foundation for the elucidation of disordered growth hormone secretion. Growth failure may result from a number of potential abnormalities in growth hormone production. Some children may have a lack of hypothalamic releasing hormone production to account for growth failure. Other children may not respond to normal amounts of the releasing hormone at the level of the pituitary gland. Still others may have some disorder in pituitary synthesis, storage or release of growth hormone. Still other children may produce a structurally altered hormone so that growth-promoting action is lost or diminished, and some may inactivate growth hormone before it reaches its site of action. Finally, some children may produce excess quantities of somatostatin which inappropriately decreases growth hormone secretion. Since human prolactin has so recently become the subject of intensive investigation, much less is known about the physiology and pathophysiology of this hormone than is known about growth hormone. Present investigations are directed at developing an understanding of the control of secretion and metabolic actions of prolactin. The objective of this project is to investigate the physiologic control mechanisms of growth hormone and prolactin storage, synthesis and release and their biochemical counterparts. Attention will be directed to the role of hypothalamic neurohormones in the control of growth hormone and prolactin release. Partial purification of growth hormone releasing hormone and prolactin release inhibiting hormone will be carried out to facilitate these studies. Furtherance of the basic understanding of pituitary function is anticipated to increase knowledge about pathologic states of pituitary function in man, to improve methods of diagnosis of hypothalamic-pituitary disorders and allow clarification of modes of therapy in states of pituitary hormonal imbalance.